Numerical study on heat transfer enhancement in a receiver tube of parabolic trough solar collector with dimples, protrusions and helical fins

Vacuum tubular receiver is the core component of parabolic trough solar collectors (PTCs). To enhance the heat transfer rate from solar radiation to heat transfer fluid (HTF), one of the effective techniques is to improve the convective heat transfer inside the inner tube. In this study, we focus the heat transfer of the HTF side. A numerical simulation on the fully developed turbulent flow and heat transfer in the inner tube with and without helical fins, protrusions and dimples has been investigated. The results show that the receiver tubes with dimples have superior performance of heat transfer augmentation compared with that with protrusions or helical fins. Then, the effects of the geometry sizes and arrangements of dimples on the convective heat transfer performance are further studied. The performance evaluation plot of heat transfer enhancement techniques show that dimples with deeper depth, narrower pitch and more numbers in the circumference direction is benefit for improving the performance of heat transfer enhancement while the varied arrangements have no obvious influence. (C) 2015 The Authors. Published by Elsevier Ltd.